Generally, metallic or rubber seals are used when connecting pipes. A rubber seal can not be used to connect pipes that conduct steam since the steam is hot and damages the rubber seal. Therefore, when connecting pipes that conduct hot material, conventionally, an annular shaped metallic packing (C-ring seal) having a C-shaped cross-section, or a C-ring seal that contains metallic spring and like were used.
An example of a metallic packing has been disclosed in Japanese Patent Application Laid-Open No. 11-101346. The annular metallic packing disclosed in this publication has an open groove that extends till the end of inner surface. This metallic packing is formed to extend a free end of inner side (open groove) in tangent line direction of outside bending part. A metallic packing with better sealing property has been disclosed in Japanese Patent Application Laid-Open No. 7-55004. The metallic packing described in this publication is O-ring seal. There is a metallic spring inside this O-ring seal and, an annular jacket that completely covers the spring.
However, the prior art metallic packings have following problems. Even if the metallic packing is used as a single body, it is difficult to determine to what extent the pipes may be tightly screwed. If the pipes are tightened too much, the elastic limit of the metallic packing may be crossed and the metallic packing may get damaged. If the metallic packing gets damaged, it looses the elasticity and does not serve the purpose. Moreover, depending on the amount of deformation of the metallic packing, it can not be removed from its place and may even damage the pipes. There is a problem with the O-ring seal with the metallic spring inside that the production cost is high.
It is an object of the present invention to provide a metallic packing having lower production cost as well as having a good sealing ability, installation ability, and high flexibility in design.